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Anterior vaginal prolapse (AVP) is the most common form of pelvic organ prolapse (POP) and has deleterious effects on women’s health. Despite recent advances in AVP diagnosis and treatment, a cell atlas of the vaginal wall in AVP has not been constructed. Here, we employ single-cell RNA-seq to construct a transcriptomic atlas of 81,026 individual cells in the vaginal wall from AVP and control samples and identify 11 cell types. We reveal aberrant gene expression in diverse cell types in AVP. Extracellular matrix (ECM) dysregulation and immune reactions involvement are identified in both non-immune and immune cell types. In addition, we find that several transcription factors associated with ECM and immune regulation are activated in AVP. Furthermore, we reveal dysregulated cell–cell communication patterns in AVP. Taken together, this work provides a valuable resource for deciphering the cellular heterogeneity and the molecular mechanisms underlying severe AVP. Anterior vaginal prolapse (AVP), the most common form of pelvic organ prolapse, has deleterious effects on women’s health. Here the authors employ single-cell RNA-seq to construct a transcriptomic atlas of vaginal wall cells from AVP patients, and find that extracellular matrix dysregulation and immune reaction are associated with AVP.

Dear Editor, N6-methyladenosine （m6A）, as the most abundant internal modification with ubiquitous feature in eukaryotic mRNAs, has been connected with many fundamental aspects of RNA metabolism such as translation [1-3], splicing [4, 5], stability and decay [6]. m6A modification is reversible and can be regulated by three groups of molecules commonly referred to as writers, erasers and readers, m6A writers are the components of the multi-complex methyltransferase catalyzing the formation of m6A methylation, among which METTL3,

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer featured with high intra-tumoral heterogeneity and poor prognosis. To comprehensively delineate the PDAC intra-tumoral heterogeneity and the underlying mechanism for PDAC progression, we employed single-cell RNA-seq (scRNA-seq) to acquire the transcriptomic atlas of 57,530 individual pancreatic cells from primary PDAC tumors and control pancreases, and identified diverse malignant and stromal cell types, including two ductal subtypes with abnormal and malignant gene expression profiles respectively, in PDAC. We found that the heterogenous malignant subtype was composed of several subpopulations with differential proliferative and migratory potentials. Cell trajectory analysis revealed that components of multiple tumor-related pathways and transcription factors (TFs) were differentially expressed along PDAC progression. Furthermore, we found a subset of ductal cells with unique proliferative features were associated with an inactivation state in tumor-infiltrating T cells, providing novel markers for the prediction of antitumor immune response. Together, our findings provide a valuable resource for deciphering the intra-tumoral heterogeneity in PDAC and uncover a connection between tumor intrinsic transcriptional state and T cell activation, suggesting potential biomarkers for anticancer treatment such as targeted therapy and immunotherapy.

The methyltransferase like 3 （METTL3）-containing methyltransferase complex catalyzes the N6-methyladenosine （m6A） formation, a novel epitranscriptomic marker; however, the nature of this complex remains largely unknown. Here we report two new components of the human m6A methyltransferase complex, Wilms＇ tumor 1-associating protein （WTAP） and methyltransferase like 14 （METTL14）. WTAP interacts with METTL3 and METTL14, and is required for their localization into nuclear speckles enriched with pre-mRNA processing factors and for catalytic ac- tivity of the m6A methyltransferase in vivo. The majority of RNAs bound by WTAP and METTL3 in vivo represent mRNAs containing the consensus m6A motif. In the absence of WTAP, the RNA-binding capability of METTL3 is strongly reduced, suggesting that WTAP may function to regulate recruitment of the m6A methyltransferase complex to mRNA targets. Furthermore, transcriptomic analyses in combination with photoactivatable-ribonucleoside-en- hanced crosslinking and immunoprecipitation （PAR-CLIP） illustrate that WTAP and METTL3 regulate expression and alternative splicing of genes involved in transcription and RNA processing. Morpholino-mediated knockdown targeting WTAP and/or METTL3 in zebrafish embryos caused tissue differentiation defects and increased apoptosis. These findings provide strong evidence that WTAP may function as a regulatory subunit in the m6A methyltransferase complex and play a critical role in epitranscriptomic regulation of RNA metabolism.

The role of Fat Mass and Obesity-associated protein （FTO） and its substrate N6-methyladenosine （m6A） in mRNA processing and adipogenesis remains largely unknown. We show that FTO expression and m6A levels are inversely correlated during adipogenesis. FTO depletion blocks differentiation and only catalytically active FTO restores adi- pogenesis. Transcriptome analyses in combination with m6A-seq revealed that gene expression and mRNA splicing of grouped genes are regulated by FTO. M6A is enriched in exonic regions flanking 5＇- and 3＇-splice sites, spatially over- lapping with mRNA splicing regulatory serine/arginine-rich （SR） protein exonic splicing enhancer binding regions. Enhanced levels of m6A in response to FTO depletion promotes the RNA binding ability of SRSF2 protein, leading to increased inclusion of target exons. FTO controls exonic splicing of adipogenie regulatory factor RUNX1T1 by regulating m6A levels around splice sites and thereby modulates differentiation. These findings provide compelling evidence that FTO-dependent m6A demethylation functions as a novel regulatory mechanism of RNA processing and plays a critical role in the regulation of adipogenesis.

Although 5-methylcytosine (m 5 C) is a widespread modification in RNAs, its regulation and biological role in pathological conditions (such as cancer) remain unknown. Here, we provide the single-nucleotide resolution landscape of messenger RNA m 5 C modifications in human urothelial carcinoma of the bladder (UCB). We identify numerous oncogene RNAs with hypermethylated m 5 C sites causally linked to their upregulation in UCBs and further demonstrate YBX1 as an m 5 C ‘reader’ recognizing m 5 C-modified mRNAs through the indole ring of W65 in its cold-shock domain. YBX1 maintains the stability of its target mRNA by recruiting ELAVL1. Moreover, NSUN2 and YBX1 are demonstrated to drive UCB pathogenesis by targeting the m 5 C methylation site in the HDGF 3′ untranslated region. Clinically, a high coexpression of NUSN2, YBX1 and HDGF predicts the poorest survival. Our findings reveal an unprecedented mechanism of RNA m 5 C-regulated oncogene activation, providing a potential therapeutic strategy for UCB. Chen et al. provide an m 5 C landscape in bladder cancer and show m 5 C enrichment at oncogene mRNAs that promotes tumour progression. They identify YBX1 as the m 5 C ‘reader’ that recruits ELAVL1 to stabilize mRNAs.

Background Vertebrate early embryogenesis is initially directed by a set of maternal RNAs and proteins, yet the mechanisms controlling this program remain largely unknown. Recent transcriptome-wide studies on RNA structure have revealed its pervasive and crucial roles in RNA processing and functions, but whether and how RNA structure regulates the fate of the maternal transcriptome have yet to be determined. Results Here we establish the global map of four nucleotide-based mRNA structures by icSHAPE during zebrafish early embryogenesis. Strikingly, we observe that RNA structurally variable regions are enriched in the 3′ UTR and contain cis -regulatory elements important for maternal-to-zygotic transition (MZT). We find that the RNA-binding protein Elavl1a stabilizes maternal mRNAs by binding to the cis -elements. Conversely, RNA structure formation suppresses Elavl1a’s binding leading to the decay of its maternal targets. Conclusions Our study finds that RNA structurally variable regions are enriched in mRNA 3′ UTRs and contain cis -regulatory elements during zebrafish early embryogenesis. We reveal that Elavl1a regulates maternal RNA stability in an RNA structure-dependent fashion. Overall, our findings reveal a broad and fundamental role of RNA structure-based regulation in vertebrate early embryogenesis.

In some insect nursery pollination mutualisms, plant hosts impose net costs to uncooperative “cheater” symbionts. These “sanctions” promote mutualism stability but their precise adaptive nature remains unclear. In fig–wasp mutualisms host trees (Ficus spp.) are only pollinated by female agaonid wasps whose larvae only use galled fig flowers as food. In actively pollinated systems, if wasps fail to pollinate, sanctions can result via fig abortion, killing all wasp offspring, or by increased offspring mortality within un-aborted figs. These sanctions result from selective investment to pollinated inflorescences, a mechanism present in almost all angiosperms. To more fully understand how selective investment functions as sanctions requires the measurement of variation in their costs and benefits to both hosts and symbionts. Gynodioecious fig-tree–fig-wasp mutualisms are particularly suitable for this because pollen and wasps are produced only in the figs of “male” trees and seeds only in the figs of “female” trees. Male and female trees thus incur different net costs of pollen absence, and costs of sanctions to pollen-free “cheater” wasps only occur in male trees. We used the actively pollinated host tree Ficus hispida and introduced into male and female figs either 1, 3, 5, 7, or 9 all pollen-laden “cooperative” (P+) or all pollen-free “cheater” (P−) wasps. Abortion in both male and female trees was highest in P− figs, with P− fig abortion higher in females (∼90%) than in males (∼40%). Fig abortion was negatively associated with foundress number mainly in P+ figs; in P− figs abortion was only weakly associated with the number of “cheater” wasps, especially in female figs. In un-aborted male figs, wasp offspring mortality was higher in P− figs than in P+ figs, and in P− figs correlated positively with foundress (cheater) number. Increased offspring mortality was biased against female wasp offspring and likely resulted from reduced larval nutrition in unpollinated flowers. Variation in selective investment to P− figs thus reflects costs and benefits of pollen absence/presence to hosts, variation that translates directly to net costs to cheater wasps.

In intimate mutualisms between hosts and symbionts, selection can act repeatedly over the development times of the interacting individuals. Although much is now known about the overall ecological conditions that favor the evolution of mutualism, a current challenge is to understand how natural selection acts on the number and kinds of partners to shape the evolution and stability of these interactions. Using the obligate fig-fig wasp mutualism, our experiments showed that the proportion of figs developed to maturity increased quickly to 1.0 as the number of foundresses increased, regardless of whether the foundresses carried pollen. Selection against pollen-free wasps did not occur at this early stage in fig development. Within figs that developed, the proportion of galls producing adult wasps remained high as the number of pollen-carrying foundresses increases. In contrast, the proportion of galls producing adult wasps decreased as the number of pollen-free foundresses increased. Viable seed production increased as the number or proportion of pollen-carrying foundresses increased, but the average number of wasp offspring per pollen-carrying foundress was highest when she was the sole foundress. These results show that figs and their pollinator wasps differ in how fitness effects are distributed throughout the development of the interaction and depend on the number and proportion of pollen-carrying foundresses contributing to the interaction. These results suggest that temporal fluctuations in the local number and proportion of pollen-carrying wasps available to enter figs are likely to have strong but different effects on the figs and the wasps.

Regeneration is the regrowth of damaged tissues or organs, a vital process in response to damages from primitive organisms to higher mammals. Planarian possesses active whole‐body regenerative capability owing to its vast reservoir of adult stem cells, neoblasts, providing an ideal model to delineate the underlying mechanisms for regeneration. RNA N6‐methyladenosine (m6A) modification participates in many biological processes, including stem cell self‐renewal and differentiation, in particular the regeneration of haematopoietic stem cells and axons. However, how m6A controls regeneration at the whole‐organism level remains largely unknown. Here, we demonstrate that the depletion of m6A methyltransferase regulatory subunit wtap abolishes planarian regeneration, potentially through regulating genes related to cell–cell communication and cell cycle. Single‐cell RNA‐seq (scRNA‐seq) analysis unveils that the wtap knockdown induces a unique type of neural progenitor‐like cells (NP‐like cells), characterized by specific expression of the cell–cell communication ligand grn. Intriguingly, the depletion of m6A‐modified transcripts grn, cdk9 or cdk7 partially rescues the defective regeneration of planarian caused by wtap knockdown. Overall, our study reveals an indispensable role of m6A modification in regulating whole‐organism regeneration. As depicted in our model, during planarian homeostasis, the expression level of grn is held at a moderate level to inhibit overgrowth, as equivalent to grn expression level before amputation at 0 hpa. Upon injury, m6A modification selectively targets several important gene transcripts, including grn for degradation, manifested as its reduced expression level after 6 hpa, as well as transcripts of cell cycle‐related genes including ccnt1, cdk7 and cdk9. m6A‐mediated downregulation of these genes, especially the grn, may halt the initial proliferation of the stem cell pool at the first stage of regeneration, which in turn promotes their differentiation process, including the differentiation of neoblasts to the progenitor cells and eventually to different tissue types. After wtap knockdown, grn transcript accumulates to form a unique cell cluster resulting in increased GRN secretion, which may lead to cell cycle dysregulation and the loss of neoblast differentiation and the failure of planarian regeneration.